Thesis (Ph.D.)--Princeton University, 2007. / (UMI)AAI3256621. Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1507.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4335. Adviser: Atul K. Jain. Includes bibliographical references (leaves 133-154). Available on microfilm from Pro Quest Information and Learning.

<p> Statistical analyses relating carbon monoxide (CO) pollution and precipitation enhancement have been performed to explain a potential weekly link in the United States of America&rsquo;s Northeast Megalopolis. I investigated the weekly relationship between CO and precipitation using instrumental records from 2009. I also investigated whether CO pollution generally affects precipitation levels in the Megalopolis. Finally, I briefly compared the patterns of precipitation and carbon monoxide in Megalopolis to see if weather systems remained isolated to the surroundings cities or moved sequentially up the Atlantic coast. </p><p> Results confirm that there was a statistically significant difference between weekday and weekend CO and precipitation levels in Baltimore and Philadelphia. There were weekly cycles in precipitation and CO in Baltimore and New York, and an overall precipitation enhancement in the Megalopolis because of CO pollution. The results also indicate a sequential movement of precipitation and CO up the Atlantic coast from Washington, D.C. toward Boston. Overall, weekly distribution patterns of CO and precipitation patterns did exist in some places in 2009, while prevailing wind patterns and CO&rsquo;s cloud nucleating capabilities may partially account for the sequential movement of CO and precipitation enhancement in the study area.</p>

<p> An observed 20-30% increase in forest net ecosystem exchange (<i> NEE</i>) on partly cloudy days is often attributed to there being more uniform canopy illumination by diffuse radiation when clouds are present. However, the sky on such days is typically populated by fair-weather cumulus clouds, bringing dynamically changing shadow-to-light conditions on the order of minutes to the forest, with radiation alternating from 1000 W m^-2 in the clear sky to less than 400 W m^-2 in under-cloud shadows. These dynamically changing conditions cannot be investigated by the conventional time-averaged eddy-covariance flux method, which requires nearly steady-state turbulent conditions over much longer 20-30-min periods in order for the fluxes to converge to stationary values. We examine the &ldquo;true&rdquo; dynamics of the whole-canopy response to the light change by using a practical ensemble-flux method applied to eddy-covariance flux measurements from two distinct forest ecosystems: Harvard Forest (HF, 42.53&deg;N, 72.17&deg;W), temperate mid-latitude forest near Petersham, Massachusetts, USA, and Tapaj&oacute;s National Forest (LBA, 2.86&deg;S, 54.96&deg;W), an Amazonian evergreen tropical forest near Santarem, Par&aacute;, Brazil. Using the rapid change in radiative flux that occurs during the transition from cloud-induced shadow to light as a reference starting point, we combine sets of conditional illumination-change shadow-to-light and light-to-shadow transition events characteristic of cumulus-cloud conditions and parametrize distributions of light and shadow durations and rates of light change of the radiative-flux time series for different cloud conditions reported by standard weather stations. We investigate the sensitivity of the dynamics of forest response to the illumination transitions initiated by these conditional events, and identify an unexpected transient <i> NEE</i> maxima when <i>NEE</i> increases above the clear-sky steady-state equilibrium values (<i>NEE</i>_eq) within the first 10 min of the light period after the shadow-to-light transition, that we hypothesize to be a physiological forest response to the abrupt light change due to presence of the intercellular CO₂ pool in the leaf tissues. Overall <i>NEE</i> builds up during the sunlit periods, but in shadow heat and water stresses are reduced, thus increasing the water use efficiency (<i>WUE</i>). To conduct this analysis, we obtain similarity criteria for realizations defined by conditional events to combine them into the ensembles. With 300 similar realizations grab-sampled at 1-s intervals, we can reliably estimate (&le; 5% standard error) dynamic ensemble fluxes resolved on a 5-s time scale. By the successful application of the first-order system of the delay differential equations with the exponential approach-to-equilibrium solutions, we are able to justify the utility of the &ldquo;Big-Leaf&rdquo;-model approach to describe whole-canopy fluxes and provide the dynamic parametrizations of the &ldquo;Big-Leaf&rdquo; Active Thermal Layer as well as of the Transient Internal Layer above both forests when the light switches on after the cloud pass. By combining results of sensitivity analysis with modelled solutions applied to the real day-long fluctuating-light time series, we show that the variable light during fair-weather clouds (Shadow period duration &lt; 100 s, Light period duration &ge; 300 s) is responsible for an increase in <i>NEE</i> above the <i>NEE</i>_eq of 15-25% for HF and 10-15% for LBA. This indicates that there is a fluctuating-light <i>NEE</i>-enhancement mechanism that can be considered to be a viable alternative to the existing hypothesis of a diffuse-radiation <i> NEE</i>-enhancement mechanism on partly-cloudy days. We show that on such days <i>Diffuse Fraction</i> can be linearly-related to <i> Cloudiness</i> estimated using the shadow-to-light change in a conditional-event radiative-flux ratio, connecting these two <i>NEE</i>-enhancement mechanisms. Combination of increased NEE with the relatively high plateau in <i>WUE</i> allows forests to operate efficiently in partly-cloudy conditions with maxima located in the <i>Cloudiness</i> range [0.1-0.3] and <i>Diffuse-Fraction</i> range [0.35-0.6], suggesting forest adaptations to the preferred lighting conditions and fair-weather cloudiness. </p><p>

<p> An experiment was designed to capture micrometeorological observations during a fire spread on a simple slope. Three towers equipped with a variety of instrumentation, an array of fire-sensing packages, and a Doppler lidar was deployed to measure various aspects of the fire. Pressure and temperature perturbations were analyzed for each of the grid packages to determine if the fire intensity could be observed in the covariance of the two variables. While two of the packages measured a covariance less than &ndash;15 &deg;C hPa, there was no clear trend across the grid. The fire front passage at each of the three towers on the slope yielded extreme swings in observed turbulent kinetic energy and sensible heat flux. Vertical velocity turbulence spectra showed that the high-intensity fire front passage at the bottom tower was 2 to 3 orders of magnitude larger than the low-intensity fire front passages at the top two towers. Opposing wind regimes on the slope caused a unique L-shaped pattern to form in the fire front. A vorticity estimation from the sonic anemometers showed that vorticity reached a maximum just as a fire whirl formed in the bend of the L-shaped fire front, leading to a rapid increase in fire spread.</p><p>

<p> This study gained novel insights into mechanistic interactions of dust and smoke particles with large-scale climate dynamics. This study revealed that the variability Saharan dust radiative properties is significantly linked to high-frequency atmospheric wave activity across the tropical Atlantic storm tracks, while the variability of smoke particles from the South African biomass burning is attributed by low-frequency oscillations of baroclinic instability of the region. </p><p> We proposed that the impacts of Saharan Air Layer (SAL) on large-scale climate dynamics mainly occur through coupling of dust radiative forcing with eddy energetics of the African easterly jet-African easterly waves (AEJ-AEWs) systems. This study quantified the thermal/mechanical impacts of oceanic SAL on activity of the AEWs and the regional feedback of eddies onto the mean-circulations from a climatological point of view. We found that both upstream and downstream developments of eddy energy are affected by oceanic SAL radiative forcing. It is suggested that dust radiative forcing has the capability to affect the transient changes in baroclinic instability of the jet-wave system through eddy available potential energy, and contribute in exchange of kinetic energy between the AEWs and AEJ through baroclinic and barotropic conversions.</p><p> This study discussed that Saharan dust radiative properties have both constructive and destructive effects on behaviors of the AEWs, which depend on structure of the waves at different time-scale: the eddy kinetic energy (EKE) of the 2&mdash;6-day ultrahigh-frequency waves are amplified in average 1-day after enhancing of dust radiative forcing, while the EKE of the 6&mdash;11-day intermediate-frequency waves weakens during dust storm events. In addition, over the western African monsoon (WAM) region and the entrance of the tropical Atlantic storm track, the 2&mdash;6-day filtered AEWs become more barotropic during oceanic SAL outbreaks. The anomalous changes in meridional and quadruple momentum fluxes of 2&mdash;6-day filtered AEWs, associated with enhanced dust in the oceanic SAL, tend to an easterly feedback onto the southern edge of the mean-AEJ. However, at the middle- to exit region of the southern storm track, the anomalous convergent momentum fluxes of 2&mdash;6-day AEWs, associated with dust outbreak, tends to increase the regional baroclinic instability through the 3 main local energy packets, which may initiate a higher chance of hurricane activity.</p><p> Applying ensemble of large NASA satellite observations data sets, such as MODIS, SeaWiFS and TRMM as well as GOCART aerosol model and MERRA reanalysis indicates that the suggested results are consistent regardless of the selected data sets. Overall, we proposed that the regional radiative properties of aerosols and thermal/mechanical activity of wave-jet systems are dynamically coupled and it is not suggested to consider either as a response to one another. </p><p>

No description available.

No description available.

No description available.

No description available.